DE69600377T2 - Partially hydrogenated aminotelechelic oligomers of 1,3-dienes and method for their preparation - Google Patents

Abstract

Oligomers of (1,3-diene) partially hydrogenated aminochelates are of formula (P)(ACH2NH2)x (I), in which X = 1.8-2; P is part of 1,3-diene oligomer containing at least 20 mol% hydrogenated double linkages of 1,2 type as in formula -CH2-C(R<1>)CH=CH2 (II); and at least 10 mol% hydrogenated double linkages of 1,4 type as in formula -CH2-CR<1>=CH-CH2- (III) where R<1> = H, 1-6C aliphatic; A = divalent group chosen from (IV) or (V) in which R<2> = 1-6C aliphatic or 3-7C cycloaliphatic; and n = 3-9. Oligomer has average molecular mass 500-5000. Also claimed is a method for the preparation of oligomers.

Description

The present invention relates to partially hydrogenated aminotelechelic liquid oligomers of 1,3-dienes which have a low viscosity at ambient temperature, and to a process for preparing these oligomers.

US Patent 2,647,146 describes the preparation of long-chain α,ω-diamines. In particular, this document relates to the synthesis of aminotelechelic oligomers of hydrogenated butadiene, which consists in preparing, in a first step, a dinitrile of the following formula:

in which n is an integer from 1 to 25, R is a generally saturated hydrocarbon radical having a carbon number of from 1 to 6 and C₄H₆- is a butadiene unit, and then, in a second step, the dinitrile (1) is hydrogenated to a primary diamine of the following formula:

The dinitrile (1) is obtained by oligomerization of butadiene in the presence of symmetrical azodinitrile in a solvent.

The diamine (2) is obtained by catalytic hydrogenation in the presence of ammonia at temperatures of 180 to 300°C and at pressures of 197 to 4934 bar. The catalyst used is a mixture of palladium on carbon and nickel on diatomaceous earth. Under these hydrogenation conditions, the butadiene units -C₄H₆- are completely converted into dihydrobutadiene units -C₄H₈ of formula (2) which consist of saturated chains of the following structures:

consist of, hydrogenated.

The products obtained are in the form of waxes at ambient temperature, which are difficult to use.

US Patent 4,920,181 also relates to the production of long-chain α,ω-diamines of the general formula

[X] (NH₂)n (3)

in which n is a number from 1.4 to 3 and X is the residue of a hydrophobic vinyl oligomer with a number average molecular weight Mn of 200 to 5000. Examples of such oligomers are oligobutadienes and oligoisoprenes as well as corresponding products with partially or fully hydrogenated double bonds. As in US Patent 2,647,146, the diamines of formula (3) are obtained in two steps.

In a first step, a cyanotelechelic oligobutadiene is prepared by bringing butadiene and a symmetrical azodinitrile into contact in a solvent (toluene) at temperatures of 90 to 130 °C under a pressure of 16 to 18 bar.

The hydrogenation of the nitrile groups of the cyanotelechelic oligobutadiene thus obtained is carried out in a solvent in the presence of ammonia and Raney cobalt in an amount of 10% by weight relative to the dinitrile to be hydrogenated. This hydrogenation takes place at a temperature of 100 to 200°C under pressures of 100 to 200 bar. These conditions enable the selective conversion of the nitrile functions into primary amine functions. It is also mentioned that the hydrogenation time is very long or that if Raney nickel is added to the Raney cobalt, the oligobutadiene double bonds can be hydrogenated to a greater or lesser extent. The hydrogenation conditions mentioned in this publication (Examples 5 to 8) are such that they lead to aminotelechelic oligobutadienes which have a high proportion of hydrogenated double bonds, so that at ambient temperature they are in the form of waxy products which are difficult to use.

Although this publication states that the double bonds can be partially hydrogenated, there is no indication of the nature of the double bonds affected. However, it is known that 1,3-dienes, especially butadiene, can undergo 1,4- and 1,2-polymerization. Furthermore, the 1,4-polymerization of butadiene leads to two different configurations:

- trans configuration:

- cis configuration:

In contrast, 1,2-polymerization leads to the formation of pendant vinyl double bonds:

There is a statistical distribution of the three structures with a mole percentage of pendant vinyl double bonds of about 20%.

However, the applicant has now found that, under certain hydrogenation conditions, it was able to hydrogenate at least 20% of the double bonds resulting from the 1,2-polymerisation of 1,3-dienes, hereinafter referred to as 1,2-type double bonds, while the double bonds resulting from the 1,4-polymerisation, hereinafter referred to as 1,4-type bonds (cis and trans), remained practically intact.

The present invention proposes a process for the preparation of partially hydrogenated aminotelechelic oligomers of 1,3-dienes containing at least 20 mol% and preferably 25 to 30 mol% of hydrogenated double bonds of the 1,2-type and have a maximum of 10 mol% and in particular less than 1 mol% of hydrogenated double bonds of the 1,4-type (cis and trans).

Furthermore, the present invention relates to partially hydrogenated aminotelechelic oligomers of 1,3-dienes of the formula

[P] (ACH₂NH₂)x (4)

in which x is a number from 1.8 to 2 and preferably practically has the value 2, P is an oligomer residue of a 1,3-diene containing at least 20 mol% of hydrogenated double bonds of the 1,2-type of the structure (a)

and not more than 10 mol% of hydrogenated double bonds of the 1,4-type (cis and trans) of structure (b)

wherein R¹ in structures (a) and (b) represents a hydrogen atom or an aliphatic hydrocarbon radical having 1 to 6 carbon atoms, A represents a divalent radical selected from the following radicals:

in which the radicals R² represent an aliphatic, linear or branched hydrocarbon radical having 1 to 6 carbon atoms or a cycloaliphatic radical having 3 to 7 carbon atoms and n represents an integer from 3 to 9, the partially hydrogenated aminotelechelic oligomer of the 1,3-diene having a number average molecular weight Mn of 500 to 5000 and preferably of 1000 to 3000.

Examples of 1,3-dienes involved in the formation of the partially hydrogenated 1,3-diene oligomer P include butadiene (R¹ = H) and isoprene (R¹ = CH₃-). The invention relates in particular to the use of butadiene.

According to the invention, the mole percentage of hydrogenated double bonds of the 1,2-type is preferably 25 to 30% and the mole percentage of hydrogenated double bonds of the 1,4-type (cis and trans) is preferably less than 1%.

Among the divalent residues of the structure

Preferred are those in which R² is isobutyl, cyclohexyl and especially methyl.

Among the divalent residues of the structure

those in which n has the value 4, 5 and 6 are preferred.

The process according to the invention for the preparation of partially hydrogenated aminotelechelic oligomers of 1,3-dienes of the formula (4) consists in the oligomerization of a 1,3-diene of the formula

in which R¹ has the meaning mentioned above, in the presence of a symmetrical azodinitrile of the formula

NC-A-N=N-A-CN (5)

where A has the same meaning as in formula (4), thereby obtaining a cyanotelechelic 1,3-diene oligomer of the formula

[P₁] (ACN)x (6)

in which P1 represents a 1,3-diene oligomer residue and A and x have the same meanings as in formula (4), followed by hydrogenation in the presence of Raney cobalt, the process being characterized in that the hydrogenation of the cyanotelechelic oligomer of 1,3-diene (6) is carried out at temperatures of from 100 to 200°C and preferably from 140 to 180°C under a hydrogen pressure of from 5 x 105; to 30 x 105; Pa and preferably from 10 x 105 to 15 x 105; Pa in the presence of a quantity of Raney cobalt of not more than 5 wt.%, based on the cyanotelechelic oligomer of the 1,3-diene used, and in the absence of ammonia.

According to the invention, the duration of the hydrogenation can vary within a wide range and is not critical. However, a hydrogenation duration of 30 hours is preferably not exceeded. This duration is preferably 2 to 25 hours. The hydrogenation reaction can be carried out in bulk or in a solvent. Preferably, an inert solvent of the aliphatic type is used, e.g. paraffins with 6 to 12 and preferably 8 to 12 carbon atoms. Examples of such compounds include octane, nonane, decane or mixtures of at least two of the compounds mentioned. Furthermore, petroleum fractions consisting of paraffinic or naphthenic hydrocarbons can be used. The use of solvents containing unsaturated, non-aromatic compounds is avoided.

The amount of Raney cobalt that can be used is at most 5% by weight, based on the cyanotelechelic 1,3-diene oligomer used. Preferably, a weight amount of 0.2 to 2.5% is used. In particular, Raney cobalt with a cobalt weight fraction of at least 80% and preferably 85 to 95% is used.

According to the invention, the hydrogenation reaction of the cyanotelechelic 1,3-diene oligomers of formula (6) is carried out in the absence of ammonia. Surprisingly, the absence of secondary and/or tertiary amines has been observed. In addition, the conversion of the nitrile groups to primary amine groups is greater than 95%. The cyanotelechelic 1,3-diene oligomers of formula (6) are known and are described in the literature. Their preparation is not the subject of the invention. These compounds can be obtained in particular by polymerizing a 1,3-diene in the presence of an initiator of the symmetrical azodinitrile type of formula (5), optionally in a solvent (acetone), at a temperature of from 60 to 140°C and under pressures of from 5 to 35 bar.

The number average molecular weight (Mn) of the cyanotelechelic 1,3-oligomer is controlled by varying the molar ratio azodinitrile/1,3-diene.

Preferably, the conditions used are such that the number average molecular weight Mn is from 500 to 5000 and preferably from 1000 to 3000.

Examples of symmetrical azodinitriles of formula (5) which can be used according to the invention are given below:

2,2'-Azobisisobutyronitrile (AIBN),

2,2'-Azobis-2-methylbutyronitrile,

2,2'-Azobis-2,4-dimethylvaleronitrile,

1,1'-azobis-1-cyclohexanecarbonitrile and

2,2'-azobiscyclohexylpropionitrile. It is preferred to use 2,2'-azobisisobutyronitrile.

According to a preferred procedure, the cyanotelechelic 1,3-diene oligomer, the solvent and the freshly prepared Raney cobalt are introduced into an autoclave equipped with a stirring device.

The mixture is then heated to a temperature of 100/120°C while introducing an inert gas such as nitrogen. After the nitrogen introduction has ended, the reaction medium is heated to a temperature of at most 200°C and preferably from 140 to 180°C. Hydrogen is then introduced, bringing the hydrogen pressure to 30 bar and preferably to 10 to 15 bar.

The temperature and pressure are maintained until a practically complete conversion (> 95%) of the nitrile groups into CH₂NH₂ groups is observed. This is easy to measure, particularly due to the alkaline nature.

After cooling, the Raney cobalt is removed by filtration. The solvent is then removed by evaporation under reduced pressure. A liquid product is obtained that is clear and almost colorless.

Under these conditions, the degree of hydrogenation of the total double bonds of the cyanotelechelic 1,3-oligomer is at most 25%.

This degree of hydrogenation can be determined in particular by the iodine number of the products obtained, which is between 250 and 400.

By ¹³C NMR analysis it is found that the degree of hydrogenation of the 1,4-type double bonds (cis and trans) is at most 10% and is generally less than 1%, while the degree of hydrogenation of the 1,2-type double bonds is at least 20% and preferably 25 to 30%.

The total degree of hydrogenation of the double bonds is preferably 5 to 15%.

The number average molar mass Mn of the partially hydrogenated aminotelechelic 1,3-oligomer obtained is a function of the number average molar mass of the cyanotelechelic 1,3-diene oligomer used.

This molecular mass Mn is 500 to 5000 and preferably 1000 to 3000.

The partially hydrogenated aminotelechelic 1,3-oligomers according to the invention have the advantage of being liquids of low viscosity and low color (color index on the GARDNER scale less than 4). They generally have viscosity values of less than 2000 mPa s at 30°C.

Their glass transition temperature measured by DSC is in the range of -85 to -75ºC.

Such oligomers can be used in particular in the synthesis of block copolymers, in the synthesis of polyureas and in polyurethane preparations as "activators" of the reactivity of hydroxylated polybutadienes.

The invention is explained below using examples.

example 1 Preparation of a cyanotelechelic 1,3-butadiene oligomer

91.08 g of 2,2'-azobisisobutyronitrile (AIBN) (0.555 mol) are placed in a 5 litre autoclave. The autoclave is then hermetically sealed and freed of oxygen. 2000 g of butadiene (36.975 mol) are then added. The reaction medium is stirred and brought to 92°C, where this temperature is maintained for 3 hours. The pressure varies from 14 x 10⁵ to 18 x 10⁵ Pa during the reaction.

After cooling the reaction medium to about 20°C, excess butadiene is removed by degassing. The clear, uncoloured residue obtained (722 g) is then placed in a rotary evaporator and any butadiene that may dissolve and any volatile impurities are removed under reduced pressure.

After filtration of the product treated in this way, 595 g of a cyanotelechelic 1,3-butadiene oligomer are obtained, which has the following physicochemical properties:

- Yield: 28%, based on the butadiene used

- Brookfield viscosity at 30ºC: 980 mPa s

- Number average molecular weight Mn, determined by gel permeation chromatography (standard): Polystyrene (converted to equivalent polybutadiene): 1380

- Iodine number = 406

The cyanotelechelic 1,3-butadiene oligomer was identified by ¹³C MR analysis on a BRUCKER apparatus (frequency for ¹³C = 75.47 MHz) using CDCl₃ as solvent.

The mole percentage of 1,4-type double bonds (cis and trans) is 79% and that of 1,2-type double bonds is 21%.

Example 2 (Invention) Hydrogenation of the cyanotelechelic 1,3-butadiene oligomer obtained in Example 1

The Raney cobalt used is Raney cobalt type A-8000 from Activated Metal and Chemicals Inc. It consists of 86 to 95% cobalt and 5 to 14% aluminum.

300 g of the cyanotelechelic 1,3-butadiene oligomer of Example 1, 45 g of octane and 6 g of Raney cobalt, ie 2% by weight with respect to the dinitrile used, are placed in a 1 liter autoclave equipped with a stirrer, a heater and temperature and pressure sensors. The Raney cobalt has previously been washed with methanol to remove most of the water it contains. The mixture is then heated to 120°C while introducing nitrogen. and maintains this temperature, which is necessary to keep the water content below 250 ppm.

The nitrogen injection is then stopped and the temperature is brought to 140ºC. Hydrogen is then introduced, bringing the total hydrogen pressure to 12 x 10⁵ Pa. The temperature and pressure are maintained for 12 hours. After this period, the -CN groups have been converted to -CH₂NH₂ groups by more than 95%. The alkalinity is measured, which in this case is 1.33 mEq HCl/g. The Raney cobalt is then removed by filtration and the octane is evaporated under reduced pressure.

A clear, slightly colored product is obtained which has a color value of 3 on the GARDNER scale and has the following physicochemical properties:

- Brookfield viscosity at 30ºC: 1300 mPa s

- Number average molecular weight Mn: 1400

- Functionality: 1.86

- Glass transition temperature, measured by differential thermal analysis: -80ºC

- Iodine number = 387

The percentage of double bonds of the 1,2- and 1,4-type (cis and trans) as well as the conversion of the -CN groups into -CH2NH2 groups are determined by NMR analysis on a BRUCKER apparatus under the same conditions as in Example 1.

In the 13C NMR spectrum of the partially hydrogenated aminotelechelic 1,3-butadiene oligomer obtained, characteristic carbon bands of CH₂NH₂ groups, which correspond to hydrogenated terminal CN groups, are observed between 50 and 56 ppm. The characteristic bands for terminal CN groups are located at approximately 125 ppm.

By integrating these bands, the degree of conversion of the -CN groups to -CH₂NH₂ groups can be determined, which in the present case is close to 95%.

The band between 10 and 12 ppm corresponds to -CH₃- groups of hydrogenated double bonds of the 1,2-type. By integrating these bands in combination with the integration of the bands, which are located at about 143 ppm and between 126 and 136 ppm and correspond to 1,2-type double bonds and 1,4-type double bonds (cis and trans), respectively, it is possible to calculate the percentage of hydrogenated 1,2-type double bonds. The percentage of -CH₂ groups due to hydrogenation of 1,4-type double bonds (cis and trans) is determined by calculation, taking into account a ratio of 21%/79% of 1,2-type and 1,4-type double bonds (cis and trans).

Thus, for the partially hydrogenated aminotelechelic 1,3-butadiene oligomer obtained under the above-mentioned hydrogenation conditions, the percentage of hydrogenated double bonds is 2% and the percentage of hydrogenated double bonds of the 1,2-type is 25.5%.

Examples 3, 4, 5 and 6 (invention)

In the following Examples 3, 4, 5 and 6, the hydrogenation of the cyanotelechelic 1,3-butadiene oligomer obtained in Example 1 is carried out.

The procedure is as in Example 2, except that various reaction parameters (pressure, temperature and percentage of Raney cobalt) are varied.

The variations of these reaction parameters as well as the physicochemical properties of the partially hydrogenated aminotelechelic 1,3-butadiene oligomers are listed in Table 1.

In this table, the percentage values for the hydrogenation of the double bonds and the nitrile groups are determined by ¹³C NMR analysis according to the calculation method given in Example 2. Table 1

Example 7 (outside the invention)

We hydrogenated the cyanotelechelic 1,3-butadiene oligomer obtained in Example 1 under the hydrogenation conditions given in US Patent 4,920,181 (Examples 5 to 8). These were the following conditions:

- Temperature T: 200ºC

- Catalyst: Raney cobalt, 10 wt.%, based on the dinitrile used

- Solvent: Toluene

- Presence of ammonia

- Total pressure: 100 x 10⁵ Pa with a partial hydrogen pressure of 70 x 10⁵ Pa and a partial ammonia pressure of 30 x 10⁵ Pa

- Hydrogenation time: 10 hours

Under these hydrogenation conditions,

- 95% of the 1,2-type double bonds are hydrogenated and

- 31.9% of the double bonds are of the 1,4-type (cis and trans)

hydrogenated.

The conversion of the -CN groups to -CH2NH2 groups was practically quantitative.

The product obtained was waxy.

Example 8

The aminotelechelic partially hydrogenated 1,3-butadiene oligomer of Example 2 (hereinafter referred to as diaminated oligomer) was tested as a reactivity activator in a polyurethane composition.

A hydroxylated polybutadiene with a functionality of 2.3 was prepared with 10 wt% of the diaminated oligomer with a functionality of 1.85. An equimolar amount of diisocyanate with respect to the -OH and -NH2 groups was added. The gelation kinetics or reaction kinetics were measured by determining the viscosity. Gel formation starts after 40 minutes when 10 wt% of diaminated oligomer is added, while in the absence of the diaminated oligomer it only starts after 80 minutes.

Under these conditions, the diaminated oligomer enables the reactivity of the polyurethane system to be doubled.

Claims (10)

1. Partially hydrogenated aminotelechelic oligomers of 1,3-dienes of the formula [P] (ACH₂NH₂)x (4), in which x is a number from 1.8 to 2 (inclusive); P is an oligomer residue of a 1,3-diene containing at least 20 mol% of hydrogenated 1,2-type double bonds of the structure (a) and not more than 10 mol% of hydrogenated double bonds of the 1,4-type (cis and trans) of structure (b) wherein R¹ in structures (a) and (b) represents a hydrogen atom or an aliphatic hydrocarbon radical having 1 to 6 carbon atoms; A represents a divalent radical selected from the following radicals: wherein the radicals R² represent an aliphatic, linear or branched hydrocarbon radical having 1 to 6 carbon atoms or a cycloaliphatic radical having 3 to 7 carbon atoms and n represents an integer from 3 to 9; wherein the oligomer (4) has a number average molecular weight Mn of 500 to 5000. 2. Oligomers according to claim 1, characterized in that the radical R¹ is a hydrogen atom. 3. Oligomers according to one of claims 1 or 2, characterized in that the mole percentage of hydrogenated double bonds of the 1,2-type is 25 to 30% and the Molar percentage of hydrogenated double bonds of the 1,4-type (cis and trans) is less than 1%. 4. Oligomers according to one of claims 1 to 4, characterized in that the radical R² is methyl. 5. Oligomers according to one of claims 1 to 4, characterized in that the number average molecular weight Mn is 1000 to 3000. 6. Process for the preparation of the partially hydrogenated aminotelechelic oligomers of 1,3-dienes of the formula (4) according to claim 1, which comprises hydrogenating a cyanotelechelic oligomer of a 1,3-diene of the formula [P₁] (ACN)x (6) in the presence of Raney cobalt, in which P1 is a 1,3-diene oligomer residue and A and x have the same meanings as in formula (4), the number average molecular weight Mn being from 500 to 5000 and preferably from 1000 to 3000, characterized in that the hydrogenation is carried out at temperatures of from 100 to 200°C under a total hydrogen pressure of from 5 x 105 Pa to 30 x 105 Pa in the presence of a quantity of Raney cobalt of at most 5% by weight, based on the cyanotelechelic oligomer of the 1,3-diene (6) used, and in the absence of ammonia. 7. Process according to claim 6, characterized in that the hydrogenation is carried out at a temperature of 140 to 180°C. 8. Process according to one of claims 5 or 6, characterized in that the hydrogenation is carried out at a total hydrogen pressure of 10 x 10⁵ Pa to 15 x 10⁵ Pa. 9. Process according to one of claims 5 to 8, characterized in that the hydrogenation is carried out in the presence of an amount of Raney cobalt of 0.1 to 2.5% by weight, based on the cyanotelechelic oligomer of the 1,3-diene used. 10. Use of the partially hydrogenated aminotelechelic oligomers of 1,3-dienes of the formula (4) according to claim 1 as reactivity activator of hydroxylated polybutadienes.